The present invention relates to a novel in-line manufacturing process for producing monolethic ceramic capacitors on elongate lead carriers or sprocketed ribbons.
Reference is made to U.S. Pat. No. 4,293,890, commonly assigned, over which the present method and products represent an improvement. The present capacitors have improved tilt-resistance under the stress of soldering the capacitors to an installation such as to a printed wiring board.
According to U.S. Pat. No. 4,293,890 a single elongate carrier or sprocketed ribbon is punched or otherwise formed to provide a base strip or ribbon supporting a plurality of integral parallel conductive leads, each having a thickness corresponding to the thickness of the carrier, a width greater than said thickness and a U-shaped clamp formed at the upper end thereof. The clamps of adjacent pairs of the conductive leads are designed to receive and hold an interposed elongate ceramic capacitor body adjacent the ends thereof in electrically-conductive contact therewith. A said capacitor body is mounted between the clamps of each adjacent pair of said leads in a direction corresponding to the length of the carrier strip, soldered thereto, dipped or coated with an insulating composition to encapsulate the body and the upper ends of conductive leads, and eventually the other ends of the conductive leads are severed from the carrier to provide individual capacitors, each having a pair of leads extending down from the same side of the capacitor body and being thinner in the direction transverse of the capacitor body than in the direction axial thereto.
The methods and products of U.S. Pat. No. 4,293,890 have many advantages. For example, the upper ends of the conductive leads have shoulder areas of enlaged width which provide an improved solder joint and which limit the length of the lead which can extend through the mounting holes of a circuit board, thereby insuring that the capacitor body will have defined standoff or spacing above the surface of the contact board to permit cleaning the areas of the board beneath the capacitor body. The distance between the shoulder areas and the capacitor body is maintained fixed and uniform by the fixed, uniform location of the base of the U-shaped clamps on the conductive leads.
However, the method and products of U.S. Pat. No. 4,293,890 have at least one inherent disadvantage. Capacitors produced according to said patent are unabalanced or non-symmetrical, and tend to tilt or bend towards the surface of the wiring board during the step of soldering the capacitors thereto. This tilting is due to the fact that the leads are offset to one side and also are thinnest and weakest in the direction perpendicular to or transverse the axis of the capacitor body, thereby giving them reduced resistance to tilting or bending in said direction and permitting the capacitor body to lay over against the surface of the writing board in spite of the presence of the lead shoulders which are designed to provide standoff.